What is 2C-B (2CB)?

2C-B is 4-bromo-2,5-dimethoxyphenethylamine, a single defined compound (C10H14BrNO2, PubChem CID 98527) first synthesised by the chemist Alexander Shulgin in 1974. It belongs to the 2C family of substituted phenethylamines, which share a common backbone and differ at the 4-position.

The single most important fact about 2C-B is what it is not. The powder sold as “tusi” or “pink cocaine” borrows the name — tusi is a phonetic rendering of “2C” — and usually contains no 2C-B at all. Energy Control, the Spanish drug-checking service, analysed 470 samples sold as tusi between 2020 and 2024: ketamine was detected in 93.2% of them and MDMA in 92.1%. 2C-B was detected in 3.6%. Those figures were reported by Abukahok, Fitzgerald and Palamar in Current Addiction Reports (2025).

So two different things share one name: a specific molecule, and a pink-dyed mixture named after it. A page, a law, a lab result or a news report may mean either. Keeping them apart is the whole point of this site, and conflating them is the most common error made about both.

The compound was sold openly in some countries in the 1980s and early 1990s under trade names before international control, which is why older references sometimes describe a legal status that no longer exists anywhere.

2C-B acts principally at serotonin receptors, and its psychedelic effects are attributed to partial agonism at the 5-HT2A receptor — the same receptor that mediates the effects of LSD, psilocybin and mescaline. It also has affinity for 5-HT2C, and a weaker interaction with adrenergic systems is the usual explanation given for its stimulant-like component at lower doses.

Its pharmacology is unusually dose-dependent, and that matters more for 2C-B than for most psychedelics. The character of the effect changes with dose rather than merely intensifying: a smaller amount is commonly described as predominantly stimulant and body-loaded with mild visual change, and a larger amount as fully psychedelic. The interval between those two is narrow compared with classic psychedelics, which is the pharmacological reason small differences in an unmeasured street dose produce very different experiences.

Because it is a partial rather than full agonist at 5-HT2A, the dose-response does not scale indefinitely, and cross-tolerance with other classic psychedelics is reported.

Public-health sources describe 2C-B as a hallucinogen with both stimulant-like and psychedelic effects that are strongly dose-dependent. Reported effects include visual distortion and colour enhancement, altered perception of time, emotional intensity, body-load, and stimulation. Nausea, anxiety, confusion, raised heart rate and raised blood pressure are commonly reported adverse effects.

Onset is typically slower than a snorted stimulant and the total duration is usually reported as several hours, shorter than LSD and closer to mescaline in character. The delayed onset is itself a documented hazard: it is the interval in which someone who feels nothing takes more, and because the dose-response is steep, redosing during onset is how a moderate dose becomes a heavy one.

Specific dose figures are deliberately not published on this page. This site does not publish dosing until it has been medically reviewed, and a dose range for a compound with a narrow window, printed next to a substance that is almost never what it is sold as, would be actively harmful. What can be said without a number: the difference between a threshold experience and an overwhelming one is small, and nobody buying an illicit powder knows which they have.

As with all classic hallucinogens, the experience is heavily shaped by dose, by the individual, and by setting.

The dominant risk is not the pharmacology of 2C-B. It is that the substance is usually something else. On the Energy Control figures above, a person buying “2C-B” on an illicit market is far more likely to receive a ketamine and MDMA mixture of unknown proportions than the compound they asked for. Every risk that follows from ketamine, from MDMA, and from combining them therefore applies to a purchase of 2C-B, and the buyer has no way to know the ratio or the dose.

Where the compound genuinely is 2C-B, reported harms include acute anxiety and panic, nausea and vomiting, cardiovascular strain, and confusion or disorientation. Interactions are a serious and under-appreciated hazard: combining a serotonergic psychedelic with MDMA, with stimulants, or with an MAOI or serotonergic antidepressant carries a risk of serotonin toxicity, and a mixture sold as tusi may contain a serotonergic drug the person did not know they were taking.

Classic hallucinogens are generally considered to have low physical-dependence potential. That says nothing about the safety of a single acute reaction, and it says nothing at all about an unidentified mixture.

Because illicit supply has no quality control, dose is unknown, purity is unknown and identity is unknown. Drug-checking, where it is available, is the only thing that narrows any of those three.

dose-dependent serotonergic; low dose relaxed/heightened senses/euphoria; medium stimulant + full intoxication; high LSD-like hallucinations + morbid delusions

20–30 min

1.5–2 hr

up to 8 hr

high-dose hallucinations/morbid delusions; persistent psychosis after single tablet; sold misrepresented as MDMA/LSD

none in US; historical pre-1995 Shulgin psychotherapy use

synthesized 1974 by Alexander Shulgin from 2,5-dimethoxybenzaldehyde; pub. w/ Carter 1975; PiHKAL "warm hug"; sold as Nexus/Erox pre-scheduling; first DEA lab ID 1986

NFLIS >1,500 reports since 1998; peak 201 (2019), 76 (2024)